The present invention relates to a device that controls elevator car speeds. More particularly, the invention relates to a centrifugally actuated governor.
A common challenge in elevator design is engineering safety systems to prevent or react to elevator malfunction. One such safety system is the speed governor. Elevator speed governors are designed to prevent elevator cars from exceeding a set speed limit. The governor is a component in an automated safety system, which is actuated when the elevator car exceeds a set speed and either signals a control system to stop the car or directly engages safeties to stop the car. One commonly known governor is a centrifugally actuated governor.
A common design of centrifugal governors used in elevator systems employs two masses, sometimes referred to as flyweights, connected kinematically in an opposing configuration by links and pinned to a tripping sheave rotating about a common axis. These interconnected parts create a governor mechanism, which rotates at an angular velocity common with the angular velocity of the sheave. The angular velocity of the rotating masses results in a centrifugal force acting to propel the masses away from the sheave axis of rotation. The movement of the masses is essentially a cantilevering motion radially outward about their pinned attachments to the sheave. A coupler prevents the radial outward movement of the masses up to a set elevator car speed. The coupler commonly includes a spring connected between the sheave and one of the masses, which resists the centrifugal force generated by the angular velocity of the rotating sheave up to a set speed. When the elevator car meets or exceeds a set speed limit, sometimes referred to as an overspeed condition, the governor is actuated. In the overspeed condition, the force of the governor coupler, for example the spring coupler, is overcome by the centrifugal force acting on the masses. The two masses move radially outward and commonly engage a sensor, which in turn signals safeties in the elevator system to slow or stop the elevator car.
There are several limitations to prior centrifugal governor designs. The governor mechanism including only two cantilevering masses leaves circumferential dead spaces in which the masses may not immediately engage the sensor after the governor is actuated, which in turn may delay the engagement of elevator safeties. The dead spaces inherent in prior centrifugal governor mechanisms create the risk of large elevator car speed increases during the period after the car reaches an overspeed condition and before safeties are engaged to slow or stop the car. The risk of large elevator car speed increments caused by the dead spaces in prior governor mechanisms creates several problems in elevator car systems. For example, large car speed increments may increase the risk of damage to system components, such as guide rails or active components of elevator safeties. Additionally, large car speed increments may cause back-up safety components to be actuated, which in some cases may make passenger rescue more time consuming and complicated.
In light of the foregoing, the present invention aims to resolve one or more of the aforementioned issues that afflict conventional governors.